Switching devices are installed in electrical circuits for connecting/disconnecting a power line to/from one or more associated electrical loads.
Known switching devices can include at least a phase, or pole, with a movable contact which is movable between a first connected position, in which it is coupled to a corresponding fixed contact (closed switching device), and a second separated position, in which it is separated from the fixed contact (open switching device). For example, if the electric load is formed by a bank of capacitors, a switching device is provided for operatively associating an AC medium voltage line to the bank of capacitors. By opening or closing the switching device, reactive power is added or removed to/from the power line.
Each phase of the switching device is electrically connected to a power line and the associated electrical load, in such a way that a current can flow between the power line and the load through the main conducting path provided by the coupled fixed and movable contacts. The flowing current is interrupted by the separation of the movable contacts from the corresponding fixed contacts, for example in case of faults.
In these known solutions, each phase of the switching device can be provided with a large number of semiconductor devices which are electrically connected in series to each other and are suitable for blocking current flowing therethrough in a blocking direction and for conducting current flowing therethrough in an allowed direction.
The overall semiconductor devices of a phase can be electrically connected in parallel to the main current path provided by the coupled movable contact and the fixed contact. The large number of semiconductor devices is due to the fact that each semiconductor device cannot withstand a tension value above a certain limit operation value, for example, at about 1 kV for standard devices.
Synchronizing the movement of the movable contact to the waveform of the alternate current flowing through the phase of the switching device, the conductive path provided by the semiconductor devices can be used for the flowing current, avoiding or at least reducing the generation of electrical arcs during the opening operation of the switching device (when the line is disconnected from a load, e.g. a bank of capacitors), and limiting an inrush current and transient voltages generated during the closing operation (when the line is coupled to the load, e.g. the bank of capacitors).
At the current state of the art, although known solutions perform satisfactorily there is still a desire for further improvements, in particular with regard to the constructive layout of the semiconducting devices and their positioning relative to the remaining parts of the switching device to which they are associated.